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Abstract Many micro-particles including pathogens strongly adhere to hosts. It remains elusive how macrophages detach these surface-bound particles during phagocytosis. We show that, rather than binding directly to these particles, macrophages form unique β2 integrin-mediated adhesion structures at the cell-substrate interfaces, specifically encircling the surface-bound particles. These circular adhesion structures that we named phagocytic adhesion rings (PARs) serve as strongholds to support local ring-shaped actin structures constricting into the particle-substrate cleavages, thereby pinching off the particles from the substrate. During this process, integrins in PARs sustain tensions due to the reaction force of actin polymerization against the particles. Such tensions are critical for phagocytic efficiency of surface-bound particles. PARs were formed in all tested macrophages (mouse, human and fish) and micron-sized particles (microbeads and E. coli), demonstrating their conserved role in the phagocytosis. This study reveals a mechanism of PAR-mediated phagocytosis, specialized for the detachment and internalization of surface-bound particles.

Abstract All-organic thermally activated delayed fluorescence (TADF) materials have emerged as potential candidates for optoelectronic devices and biomedical applications. However, the development of organic TADF probes with strong emission in the longer wavelength region (> 600 nm) remains a challenge. Strong π-conjugated rigid acceptor cores substituted with multiple donor units can be a viable design strategy to obtain red TADF probes. Herein, 3,6-di-t-butyl carbazole substituted to a dibenzopyridoquinoxaline acceptor core resulted in a T-shaped donor–acceptor–donor compound, PQACz-T, exhibiting red TADF in polymer-embedded thin-films. Further, PQACz-T self-assembled to molecular nanoaggregates of diverse size and shape in THF–water mixture showing bright red emission along with delayed fluorescence even in an aqueous environment. The self-assembly and the excited-state properties of PQACz-T were compared with the nonalkylated analogue, PQCz-T. The delayed fluorescence in nanoaggregates was attributed to the high rate of reverse intersystem crossing. Moreover, an aqueous dispersion of the smaller-sized, homogeneous distribution of fluorescent nanoparticles was fabricated upon encapsulating PQACz-T in a triblock copolymer, F-127. Cytocompatible polymer-encapsulated PQACz-T nanoparticles with large Stokes shift and excellent photostability were demonstrated for the specific imaging of lipid droplets in HeLa cells.

Tuning the fluorescence of π-conjugated small organic molecules through the structural modifications and in the presence of external stimuli have found immense applications ranging from sensing, switching, optoelectronics to bioimaging. Herein, we demonstrated a simple design strategy for the synthesis of a pyrene-cyanostyrene-pyridine molecular triad (PYBNP) using a cost-effective, one-step Knoevenagel condensation between 1-pyrenecarboxaldehyde and 2-(4-(pyridin-4-yl)phenyl)acetonitrile. PYBNP exhibited strong solid-state emission having a quantum yield of ∼ 36 ± 3% due to the deactivation of nonradiative decay channels through the restriction of intramolecular rotations and reduced π-π stacking interactions as revealed from the crystal structure analysis. Similarly, PYBNP was found to be highly emissive in the constrained environments like viscous medium and aggregated state. The optical properties of PYBNP could be tuned by the UV light-mediated dynamic Z/E-isomerization as elucidated through fluorescence spectroscopy and NMR analysis. Additionally, the pyridinic nitrogen centre allowed the fabrication of methylated analog (PYBNPM; a new cationic photoresponsive species). The cationic PYBNPM showed a better solvatochromic behavior contrary to PYBNP due to the efficient intramolecular charge transfer (ICT). The different crystal packing of PYBNP and that of hexafluorophosphate salts of PYBNPM led to distinct fluorescent properties in the solid-state. As a preliminary exploration, the cationic PYBNPM(PF6) was employed for the specific imaging of the mitochondria through multiple fluorescence channels in an aqueous medium. The cost-effective and viable design strategy demonstrated for the fabrication of a simple molecular triad holds the promise for the emergence of new functional fluorescent molecules to molecular materials for task-specific applications.

Many micro-particles including pathogens strongly adhere to hosts. It remains elusive how macrophages detach these surface-bound particles during phagocytosis. We show that, rather than binding directly to these particles, macrophages form unique β2 integrin-mediated adhesion structures at the cell-substrate interfaces, specifically encircling the surface-bound particles. These circular adhesion structures that we named phagocytic adhesion rings (PARs) serve as strongholds to support local ring-shaped actin structures constricting into the particle-substrate cleavages, thereby pinching off the particles from the substrate. During this process, integrins in PARs sustain tensions due to the reaction force of actin polymerization against the particles. Such tensions are critical for phagocytic efficiency of surface-bound particles. PARs were formed in all tested macrophages (mouse, human and fish) and micron-sized particles (microbeads and E. coli), demonstrating their conserved role in the phagocytosis. This study reveals a mechanism of PAR-mediated phagocytosis, specialized for the detachment and internalization of surface-bound particles. It remains elusive how macrophages internalize surface-bound particles. Here, authors discover an adhesion complex at the cell-substrate interface, which coordinates with F-actin to dislodge particles from the surface. [ABSTRACT FROM AUTHOR]

The document is a contents list for the journal CrystEngComm, which focuses on solid-state and crystalline materials. It includes information about the articles and papers in the issue, as well as details about the journal's editorial board. The journal welcomes studies on various aspects of crystal behavior and engineering. The article in this issue explores the electrocatalytic hydrogen production activity of a copper(II)-dipyridylamine complex in acidic water. The authors conducted experiments to investigate the efficiency of this complex in generating hydrogen gas, providing valuable insights into its potential as a catalyst for hydrogen production. [Extracted from the article]

A water-stable and structurally-characterized earth-abundant copper(II) complex, [Cu(dpa)2(N3)]Cl·4H2O, containing an N,N-chelator (dpa = 2,2′-dipyridylamine) and an ancillary ligand (N3− = azide ion) was synthesized and evaluated for electrocatalytic H2 production activity in water using acetic acid as a proton source. Crystal engineering approach revealed the presence of multiple lattice water molecules and a chloride ion in the secondary coordination zone of the distorted square pyramidal copper(II) complex forming an 8-membered tetrameric water cluster and, subsequently, an 11-membered hexameric water cluster in a repetitive mode in association with a water-chloride cluster, leading to a beautiful long-range supramolecular framework involving the chains of a copper(II) complex. The copper catalyst exhibited excellent hydrogen generation activity for the electrochemical proton reduction in acidic water with a rate of 49.81 s−1. A Faradic efficiency of 71% was derived from controlled potential electrolysis (CPE) with [Cu(dpa)2(N3)]+ at −1.25 V vs. Ag/AgCl for 3 h using a glassy carbon electrode ensuring a high turnover number of 41.96 and the desired durability of the molecular electrocatalyst under electrochemical conditions. Further, electrochemical, spectroscopic, and computational studies propose the proton-coupled reduction mechanism for the hydrogen evolution where endo conformational Hδ+⋯Hδ− coupling effectively releases molecular hydrogen. [ABSTRACT FROM AUTHOR]

The properties and functions of non-covalent interaction-driven fluorescent supramolecular self-assembly depend greatly on their evolution dynamics. Electron microscopy, atomic force microscopy, and confocal laser scanning microscopy have been used to elucidate the formation of molecular self-assembly. However, some pertinent issues, such as the drying or freezing of the sample for electron microscopy, the influence of the interactions between the tip and the sample in atomic force microscopy imaging, and the low spatial resolution of confocal laser scanning microscopy images, often impede the real-time analysis and exploration of the dynamics of molecular self-assembly processes. In this context, fluorescence correlation spectroscopy and fluorescence lifetime imaging microscopy have recently been explored to unravel the physical picture of the in situ growth dynamics and stimuli-induced morphological transformation of luminescent self-assembled structures. The current highlight article demonstrates the need for fluorescence correlation spectroscopy and fluorescence lifetime imaging microscopy to acquire precise information on the dynamics and morphological evolution of fluorescent self-assembled architectures using a few remarkable recent studies. In addition to the current status and challenges, the future directions for the further exploration of dynamic self-assembly processes towards developing next-generation functional materials have been delineated. [ABSTRACT FROM AUTHOR]

We report the photophysical properties, self‐assembly and biological evaluation of an isothiazolanthrone‐based dye, 7‐amino‐6H‐anthra[9,1‐cd]isothiazol‐6‐one (AAT), which reveals anticancer properties and can be potentially used as dye for monitoring cell viability. The solvent‐dependent photophysical studies suggest that the emission of AAT is sensitive to environment polarity due to which interesting changes in the colored emission may be observed owing to the charge transfer (CT) processes. AAT also self‐assembles to tree‐like branched morphologies and produce, a greenish emission inside the cells when imaged after short interval (15 mins) of incubation while a red fluorescence could be noted after 24 h. Interestingly, AAT also produce differential emission inside mouse normal cells as compared to its cancer cell lines since it possess anticancer activity. The experimental observations were also validated theoretically via computational modeling. [ABSTRACT FROM AUTHOR]

This study highlights the design, synthesis, spectroscopic characterization and catalytic phosphoesterase cleavage activity of two isostructural and isomorphous complexes, [Cu(L)]4 (1) and [Ni(L)]2·CH3OH (2) containing a new synthetic N,N-type donor ligand, namely 1,3-bis(((E)-(1H-pyrrol-2-yl)methylene)amino)propan-2-ol (H2L). The ligand, H2L has been synthesized by coupling of pyrrole-2-carboxaldehyde and 1,3-diamino-propane-2-ol under reflux. X-Ray crystallography study reveals that both the Cu(II) and Ni(II) centres in 1 and 2 adopt nearly a perfect square planar geometry and they display a high degree of similarity in their structural features. The biocatalytic fate of the complexes has been evaluated towards the hydrolytic cleavage of the phosphoester linkage in an aqueous DMF medium at room temperature. The spectrophotometric studies favour a higher turnover frequency for the hydrolysis of phosphoester bonds for the copper(II) complex (kcat, 1.56 × 104 h−1) over the nickel(II) complex (kcat, 5.61 × 103 h−1). Electrochemical, spectrophotometry, electron spray ionization mass spectrometry and detailed density functional theory studies illuminate the mechanistic interpretation attributing the crucial role of coordinated water, facilitating the nucleophilic attack on the phosphorous centre of pNPP, and shed light on mechanistic aspects for the efficient hydrolysis of phosphoester substrates for the copper complex over the nickel complex. [ABSTRACT FROM AUTHOR]

A photo‐switchable ionophore, (E)‐4‐([2‐hydroxy‐3‐methoxybenzylidene]amino)‐1,5‐dimethyl‐2‐phenyl‐1,2‐dihydro‐3H‐pyrazol‐3‐one (S1), was rationally designed and developed for the visible light‐triggered selective and efficient transport of Al (III) ions. The non‐fluorescent probe distinctly manifests its green light at 518 nm in presence of Al (III) ion upon irradiation at 405 nm and showed a turned‐off emission with EDTA in ethanol. The binding mode and structural perspective of S1 were assessed through X‐ray crystallography, spectrophotometry, spectrofluorimetry, 1H nuclear magnetic resonance (NMR) titration, electrospray ionization mass spectrometry (ESI‐MS) analysis and computational calculations, suggesting a 1:1 binding stoichiometry and a distorted tetrahedral coordination geometry of S1‐Al complex. The testing strip was also developed with S1 coating for colourimetric and naked‐eye detection of Al (III) ion as evident from the green fluorescence upon irradiation at 365 nm. Further, a bioimaging study of S1 in human colon living cells (HP‐29) revealed the presence of Al (III) ion through a bright green fluorescence in HP‐29, indicating the potentiality of S1 to trace Al (III) in living cells. Additionally, cytotoxicity studies by MTT assay and staining analysis ensured that the probe might be an efficient and sensitive chemosensor for monitoring Al (III) ion in drug delivery and biological applications. [ABSTRACT FROM AUTHOR]

Porous organic polymers (POPs) have received increasing attention due to their properties, such as permanent porosity with tunable pore size, robust structure, high surface area, and versatility of the backbone for the desired function. Such properties prove to be quite valuable for a plethora of sustainable applications. POPs can largely be classified as crystalline or amorphous based on the degree of long-range order. Crystalline POPs such as two-dimensional covalent organic frameworks possess characteristics such as unimodal pores with long one-dimensional pore channels allowing size-selective guest recognition, whereas amorphous network POPs give rise to a hierarchical pore size distribution enabling facile ion and mass transport. Since structure plays an undeniably vital role in the function, POPs with contrasting degrees of long-range order are suitable for some applications more than others. To address this conundrum, here we discuss at length the impact of the extent of structural order of the POPs in the context of four key applications, namely water treatment, electrochemical energy storage, heterogeneous catalysis, and optical sensing along with light-harvesting. Additionally, the formation principles of POPs with varying degrees of long-range order in view of kinetics and thermodynamics have been outlined. Furthermore, we provide a general guideline for the specific use of crystalline and amorphous POPs along with future avenues of exploration mitigating the current challenges towards the design of task-specific new-generation functional porous materials. [ABSTRACT FROM AUTHOR]

The development of luminescent probes has gained significant interest in real-time intracellular sensing and imaging of various biologically relevant species. The accuracy in sensing and imaging circumventing the background signals due to autofluorescence is essential to decipher subtle changes in cellular microenvironments under diverse pathophysiological conditions. In this context, luminescent probes for background-free imaging demands rational molecular design strategies along with various optical features like lower energy and multiphoton excitation, larger Stokes or anti-Stokes shift, and long-lived emission. Multiphoton microscopy employing two-photon absorbing molecular materials and upconversion nanoprobes is beneficial for deep-tissue imaging. In contrast, organic long-lived emissive probes, including thermally activated delayed fluorescence and room temperature phosphorescence materials, provide promising scope for time-gated imaging, ruling out the dependency on probe concentration and laser power. On the other hand, bioluminescent and chemiluminescent molecular probes producing excited-state emissive species without any optical excitation are emerging candidates for autofluorescence-free intracellular sensing and imaging. In this review article, we delineate versatile design strategies, including the choice of luminescent cores, targeting units, and sensing sites, for the development of multifunctional probes with improved intracellular sensing and imaging. Moreover, a brief discussion of different photophysical pathways involved in signalling processes is provided. The current challenges in targeted intracellular delivery of the probes for non-invasive sensing and imaging are indicated. Finally, we emphasize the future prospects of multiphoton excitable or self-illuminating long-lived emissive probes with state-of-the-art super-resolution microscopy techniques for intracellular sensing and imaging with nanoscale resolution. [ABSTRACT FROM AUTHOR]

A new bio-active Schiff base was synthesized from cinnamaldehyde and aniline and the Zn(II), Ni(II) metal complexes have been synthesized and structurally characterized by micro-analytical, magnetic property, conductivity, mass spectra, FT-IR, Electronic absorption spectra, ¹H-NMR, and 13C-NMR spectral studies. The Physico-chemical and spectral data show that the complexes have the composition of 1:1 type of metal with a ligand. Its electronic absorption spectra and magnetic study proposed the tetrahedral geometry for Zn(II) complex and octahedral geometry for Ni(II) complex. It was further supported by the mass and IR spectra; the biological activities of Schiff base and their metal complexes were carried out by the Agar disc diffusion method. The results confirmed that the metal complexes enhanced the bio-potential activities than the free Schiff base. [ABSTRACT FROM AUTHOR]

A π-conjugated porous organic polymer (BCzBz) was fabricated employing N,N′-bicarbazole and benzothiadiazole as molecular building units exhibiting broad visible light absorption. The photostable, water-dispersible, and cytocompatible BCzBz was demonstrated as an efficient probe for intracellular reactive oxygen species generation under photoirradiation. [ABSTRACT FROM AUTHOR]

Frontispiece: Molecular Engineering Approaches Towards All-Organic White Light Emitting Materials Keywords: fluorescence; molecular engineering; noncovalent interactions; single molecules; white light emission EN fluorescence molecular engineering noncovalent interactions single molecules white light emission 1 1 1 05/06/20 20200504 NES 200504 B White light emitting (WLE) materials are of increasing interest b owing to their promising applications in artificial lighting, display devices, molecular sensors, and switches. Fluorescence, molecular engineering, noncovalent interactions, single molecules, white light emission. [Extracted from the article]

White light emitting (WLE) materials are of increasing interest owing to their promising applications in artificial lighting, display devices, molecular sensors, and switches. In this context, organic WLE materials cater to the interest of the scientific community owing to their promising features like color purity, long‐term stability, solution processability, cost‐effectiveness, and low toxicity. The typical method for the generation of white light is to combine three primary (red, green, and blue) or the two complementary (e.g., yellow and blue or red and cyan) emissive units covering the whole visible spectral window (400–800 nm). The judicious choice of molecular building blocks and connecting them through either strong covalent bonds or assembling through weak noncovalent interactions are the key to achieve enhanced emission spanning the entire visible region. In the present review article, molecular engineering approaches for the development of all‐organic WLE materials are analyzed in view of different photophysical processes like fluorescence resonance energy transfer (FRET), excited‐state intramolecular proton transfer (ESIPT), charge transfer (CT), monomer‐excimer emission, triplet‐state harvesting, etc. The key aspect of tuning the molecular fluorescence under the influence of pH, heat, and host–guest interactions is also discussed. The white light emission obtained from small organic molecules to supramolecular assemblies is presented, including polymers, micelles, and also employing covalent organic frameworks. The state‐of‐the‐art knowledge in the field of organic WLE materials, challenges, and future scope are delineated. [ABSTRACT FROM AUTHOR]

The current study demonstrates a simple and economical synthetic approach for the development of a multifunctional Schiff base compound (NRSB) through the condensation reaction between 2-hydroxynaphthaldehyde and a five-membered heterocycle 3-aminorhodanine. The rhodanine unit was chosen due to the presence of an active electron-deficient carbonyl group. A facile chemical transformation from the closed to the open form was noticeable for rhodanine derivatives in the presence of a suitable nucleophile or an electron-rich system. Such a unique feature was invoked to develop a versatile molecular platform for the colorimetric sensing of methanol and the fluorometric detection of Al3+ ions. The nucleophilic attack by methanol on NRSB led to the formation of an open-ring compound, NRSB-O, with a distinct change in color from colorless to yellow. NRSB showed noticeable sensitivity towards methanol and the detection limit was found to be 0.43 wt%. The methanol-induced chemical transformation from NRSB to NRSB-O was probed through X-ray diffraction studies. The strong CH–π interaction between the methylene protons of the rhodanine unit and the π-electron cloud of the naphthalene unit (3.03 Å) and the π–π interaction between naphthalene and the rhodanine moiety (3.51 Å and 3.55 Å) lead to a two-dimensional (2D) supramolecular structure in the NRSB crystal. NRSB-O possesses strong CH–π interactions between molecules with an intermolecular distance of 2.49 Å, leading to 2D-supramolecular self-assembly. The crystal structure revealed the scope of the chelation of NRSB-O with metal ions due to the presence of different N, O, and S donor centers. Interestingly, NRSB-O exhibited a turn-on fluorescence response specifically towards Al3+ through the chelation-enhanced fluorescence (CHEF) mechanism over other competitive metal ions. The turn 'on–off' fluorescence switching was demonstrated for multiple cycles through the alternative addition of Al3+ and EDTA. The low-cost, simple design strategy of NRSB and NRSB-O as delineated in the current study would contribute to further development of task-specific molecular sensors and switches. [ABSTRACT FROM AUTHOR]

The present study demonstrates the tuning of iconic optical features of pyrene through its judicious assembly with a C3-symmetric triaminoguanidinium ion, leading to the development of a unique multifunctional luminescent material PYTG. By fine tuning the concentration and the external stimuli, such as temperature, the addition of analytes led to a dramatic change in the fluorescence of PYTG, providing an excellent platform for the exploration of the dynamic and static excimer formation. Recently, white-light-emitting molecular probes have received considerable attention from the scientific community due to their great potentials in display devices. Tripodal PYTG was employed as a pure white-light emitter consisting of blue emission from monomers and orange emission from excimers both in solution and thin film with Commission Internationale de l’Eclairage (CIE) coordinates of (0.33, 0.34) and (0.33, 0.38), respectively. The formation of a dynamic excimer along with monomer fluorescence at higher concentrations of PYTG led to tunable emission. Additionally, the rich electronic properties of PYTG allowed efficient detection of trivalent metal ions by turn-on fluorescence and colorimetric sensing of fluoride ions. PYTG selectively detected Fe3+ and Al3+ with nanomolar sensitivity in a semi-aqueous solution via a chelation-enhanced fluorescence response in the orange-red region (λem = 588 nm) by static excimer formation. The ‘on–off’ fluorescence switching by the consecutive addition of trivalent cations and a chelating ligand EDTA makes PYTG a promising fluorescent molecular switch. A simple and cost-effective strategy, leading to the development of a versatile fluorescent probe and an in-depth exploration of the structure–property relationship as delineated in the present manuscript, will pave the way for the emergence of novel task-specific molecular optical materials. [ABSTRACT FROM AUTHOR]

A novel approach for the fabrication of a solution processable conjugated porous organic polymer (CzBDP) involving a flexible core composed of carbazole and boron dipyrromethene was developed. The red emitting soluble polymer was found to be an excellent probe for the generation of both singlet oxygen and superoxide anion radicals under visible light irradiation. [ABSTRACT FROM AUTHOR]

Abstract: Generating intense upconversion photoluminescence from a single‐phase nanocrystal is a fundamental problem. Herein, we report engineered NaYF4 nanocrystals capable of converting NIR (980 nm) excitation into sharp and diverse emissions in the UV‐Vis‐NIR regions, which is desirable for triggering multiple photoactive agents for enhanced photo‐theranostics. This unique emission profile is used for NIR‐induced photo‐theranostic applications by developing a nanoplatform with a white‐emitting NaYF4 (WEN) core, with comparable blue, green and red emissions, and a mesoporous silica shell decorated with two different photosensitizers (PSs), Rose Bengal (hydrophilic) and zinc(II)phthalocyanine (hydrophobic) to utilize green and red emissions, respectively. A chemical assay demonstrates efficient generation of 1O2 under NIR excitation by the dual PS nanoplatform compared to the conventional systems. Furthermore, NIR‐induced ROS generation leads to the enhanced photodynamic destruction of cancer cells (HeLa) in vitro. The white light from the nanoplatform is also utilized in cellular bioimaging. Unlike the previously reported upconversion probes, which required sophisticated imaging setups, the high intensity white light emission from this nanoplatform allows the probing of animal cells by a digital camera attached externally to an optical microscope. This is the first report on the theranostic application of a white‐light‐emitting photoluminescent nanomaterial. [ABSTRACT FROM AUTHOR]